https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109385
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- clang rejects it with: <source>:4:16: error: expression contains unexpanded parameter pack 'vals' return [=]() { ^ <source>:9:10: error: variable has incomplete type 'void' auto result = sort_fn(); ^